Computing an Indicator

We have now run the simulation, so let's explore the results. UrbanSim supports the concept of ``indicators'' that are useful representations of dataset attributes. Conceptually, an indicator is a variable that conveys information on the condition or trend of an attribute of the system considered. When we calculate the indicator with a particular set of data, we produce an indicator result. We can then view the indicator result with an indicator visualization, such as a map, comma-separated-value file, or a tab-delimited file for use by another program.

First, let's produce a simple map (don't get too excited, it is only an image map -- we're working on fancier maps with ArcGIS and other systems too, but this is a quick visualizer that doesn't have all the overhead of a GIS).

1. On the left side of the GUI window, select the ``Results Manager'' tab. This tab displays a number of indicators and the results of computations done on them. The top-level ``Libraries'' node has a number of ``indicator_library'' type subnodes. These nodes represent libraries of indicators. Their subnodes, are the indicators. The top-level ``Data_sources'' node contains data about the various runs available. It is outside the scope of this tutorial. The top-level node ``Results'' has a number of subnodes which are ``indicator results'' -- the results of an indicator computation on particular data.

2. Right-click on the ``population'' indicator under ``Libraries > model.gridcell'' and select ``Generate results with...'' This will open a tab on the right side of the GUI which allows you to specify parameters for generating a particular result.

3. Now we will actually perform the indicator computation. In the ``Generate results'' tab, choose the value ``population'' from the ``Indicator'' drop-down menu. From the ``Dataset'' drop-down menu, choose ``gridcell'', and from the ``Source data'' drop-down menu, choose ``eugene_baseline''. Finally, click the ``Generate results...'' button. In the log window below the button you will see a small amount of log output about the indicator calculation.

4. Now we display the results. In the ``Results Manager'' tab, scroll down to the ``Results'' node. Find the subnode called ``population.gridcell.eugene_baseline'' and right-click on it. Select ``View results as...> Map (Matplotlib)''. This will cause a tab called ``gridcell_map_1980_gridcell_population'' to pop up in the right side of the GUI. This tab will display the resultant map. Caution: in this prototype version of the GUI, there are other possible results displayed -- these aren't hooked up to anything yet. Just use the ``population.gridcell.eugene_baseline'' node.

5. You can also compute the results at different geographies. In the ``Generate results'' tab, as before right-click on the ``population'' indicator under ``Libraries > model.gridcell'' and select ``Generate results with....'' Again this will open a tab on the right side of the GUI which allows you to specify parameters for generating a particular result. This time, choose the value ``population'' as before, but from the ``Dataset'' drop-down menu, choose ``zone'' instead of ``gridcell.'' From the ``Source data'' drop-down menu, choose ``eugene_baseline'' as before, and click the ``Generate results...'' button.

6. Now let's display the results as a table of zones. (You probably don't want to have a table of gridcells, since there are so many.) Right-click on the ``population.zone.eugene_baseline'' node under ``Results''. Now select ``Table (one per selected indicator)''. A table will pop up on the right side of the GUI. Caution: right now the map visualization won't work for zones, just gridcells -- so for zones just view these as a table.